A way to bake your unity terrain trees into the nav mesh

TreeObstacleBaker.cs

///////////////////////////////////////////////////////////////////////////////
// 
// This code is licensed under MIT license.
// 
// Copyright © 2026 Bil Simser, https://www.simstools.com
//
// Permission is hereby granted, free of charge, to any person obtaining a copy 
// of this software and associated documentation files (the "Software"), to 
// deal in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is 
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in 
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
///////////////////////////////////////////////////////////////////////////////

using UnityEditor;
using UnityEngine;
using UnityEngine.AI;

///////////////////////////////////////////////////////////////////////////////
///
/// 1. Make sure your tree prefab has a collider
/// 2. Go to your tool bar and click the obstacle baker. This will spawn a 
///    capsule game object at every tree under a parent game object. 
/// 3. Bake your nav mesh surface
/// 4. Delete the Obstacle object
///
///////////////////////////////////////////////////////////////////////////////
public class TreeObstacleBaker : EditorWindow
{
    [MenuItem("Tools/Bake Trees With Temporary Capsules")]
    public static void ShowWindow()
    {
        GetWindow<TreeObstacleBaker>("Tree Obstacle Baker");
    }

    private void OnGUI()
    {
        GUILayout.Label("Bake Terrain Trees into NavMesh (temporary capsules)", EditorStyles.boldLabel);
        EditorGUILayout.Space(10);

        if (GUILayout.Button("Generate Capsules for Trees"))
        {
            GenerateTreeCapsules();
        }
    }

    private void GenerateTreeCapsules()
    {
        Terrain terrain = Terrain.activeTerrain;
        if (terrain == null)
        {
            Debug.LogError("No active terrain found.");
            return;
        }

        TreeInstance[] trees = terrain.terrainData.treeInstances;
        if (trees.Length == 0)
        {
            Debug.LogWarning("No trees found on the terrain.");
            return;
        }

        // Remove previous obstacles
        GameObject oldParent = GameObject.Find("Tree_Obstacles");
        if (oldParent != null) DestroyImmediate(oldParent);

        GameObject parent = new GameObject("Tree_Obstacles");
        Undo.RegisterCreatedObjectUndo(parent, "Create Tree Obstacles");

        int createdCount = 0;

        foreach (TreeInstance tree in trees)
        {
            // Convert tree local position to world
            Vector3 worldPos = Vector3.Scale(tree.position, terrain.terrainData.size) + terrain.transform.position;

            GameObject capsule = GameObject.CreatePrimitive(PrimitiveType.Capsule);
            capsule.name = "TreeCapsule_" + createdCount;
            capsule.transform.position = worldPos;
            capsule.transform.SetParent(parent.transform);

            // Adjust scale (example: 1 unit radius, height = terrain tree height)
            float treeHeight = terrain.terrainData.size.y * 0.5f; // adjust as needed
            capsule.transform.localScale = new Vector3(1f, treeHeight / 2f, 1f); // height in Unity capsule = scale.y * 2
            capsule.isStatic = true; // mark as static for NavMesh baking

            // Remove collider if desired after bake
            // Or leave it for baking
            // Collider col = capsule.GetComponent<Collider>();

            createdCount++;
        }

        Debug.Log($"Created {createdCount} tree capsules. Bake NavMesh now and then you can delete the parent object.");
    }
}